Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.32	9.474%	$109.8243	$109.82	$109.80	$109.80
Purchase #2	$25.51	10.405%	$28.1643	$28.16	$28.15	$28.20
Purchase #3	$48.41	10.729%	$53.6039	$53.60	$53.60	$53.60
Purchase #4	$51.62	3.464%	$53.4081	$53.41	$53.40	$53.40
Purchase #5	$240.48	4.260%	$250.7244	$250.72	$250.70	$250.70
Purchase #6	$154.64	13.758%	$175.9154	$175.92	$175.90	$175.90
Purchase #7	$224.34	6.309%	$238.4936	$238.49	$238.50	$238.50
7 purchase totals =	$845.32		$910.1340	$910.12	$910.05	$910.10